82-609: The Franz Josef Glacier ( Māori : Kā Roimata o Hine Hukatere ; officially Franz Josef Glacier / Kā Roimata o Hine Hukatere ) is a 12-kilometre-long (7.5 mi) temperate maritime glacier in Westland Tai Poutini National Park on the West Coast of New Zealand's South Island . Together with the Fox Glacier 20 kilometres (12 mi) to the south, and a third glacier, it descends from
164-424: A cirque landform (alternatively known as a corrie or as a cwm ) – a typically armchair-shaped geological feature (such as a depression between mountains enclosed by arêtes ) – which collects and compresses through gravity the snow that falls into it. This snow accumulates and the weight of the snow falling above compacts it, forming névé (granular snow). Further crushing of the individual snowflakes and squeezing
246-510: A cyclic pattern of advance and retreat, driven by differences between the volume of meltwater at the foot of the glacier and volume of snowfall feeding the névé. Over the past 14,000 years glaciers worldwide have generally retreated. Most of New Zealand's large glaciers shrank significantly towards the end of the 20th century, a consequence of global warming . However, in the Southern Alps warmer temperatures cause increased precipitation on
328-522: A glacier is usually assessed by determining the glacier mass balance or observing terminus behavior. Healthy glaciers have large accumulation zones, more than 60% of their area is snow-covered at the end of the melt season, and they have a terminus with a vigorous flow. Following the Little Ice Age 's end around 1850, glaciers around the Earth have retreated substantially . A slight cooling led to
410-601: A glacier may flow into a body of water, it forms only on land and is distinct from the much thinner sea ice and lake ice that form on the surface of bodies of water. On Earth, 99% of glacial ice is contained within vast ice sheets (also known as "continental glaciers") in the polar regions , but glaciers may be found in mountain ranges on every continent other than the Australian mainland, including Oceania's high-latitude oceanic island countries such as New Zealand . Between latitudes 35°N and 35°S, glaciers occur only in
492-411: A glacier via moulins . Streams within or beneath a glacier flow in englacial or sub-glacial tunnels. These tunnels sometimes reemerge at the glacier's surface. Most of the important processes controlling glacial motion occur in the ice-bed contact—even though it is only a few meters thick. The bed's temperature, roughness and softness define basal shear stress, which in turn defines whether movement of
574-408: A kilometer per year. Eventually, the ice will be surging fast enough that it begins to thin, as accumulation cannot keep up with the transport. This thinning will increase the conductive heat loss, slowing the glacier and causing freezing. This freezing will slow the glacier further, often until it is stationary, whence the cycle can begin again. The flow of water under the glacial surface can have
656-404: A large effect on the motion of the glacier itself. Subglacial lakes contain significant amounts of water, which can move fast: cubic kilometers can be transported between lakes over the course of a couple of years. This motion is thought to occur in two main modes: pipe flow involves liquid water moving through pipe-like conduits, like a sub-glacial river; sheet flow involves motion of water in
738-460: A lower heat conductance, meaning that the basal temperature is also likely to be higher. Bed temperature tends to vary in a cyclic fashion. A cool bed has a high strength, reducing the speed of the glacier. This increases the rate of accumulation, since newly fallen snow is not transported away. Consequently, the glacier thickens, with three consequences: firstly, the bed is better insulated, allowing greater retention of geothermal heat. Secondly,
820-526: A maximum in the early 18th century. When Haast became the first European to see the glacier it was still much longer than today, and the ice surface was 300 m higher. Between its first official mapping in 1893 and a century later in 1983, Franz Josef Glacier retreated 3 km up the valley. There were several periods of advance in the 20th century – 1946 to 1951 (340 m), 1965 to 1967 (400 m), 1983 to 1999 (1420 m) and 2004 to 2008 (280 m) – but all were followed by periods of greater retreat. This cyclic behaviour
902-441: A moraine 9000 years ago, while Peters Pool close to the glacier's face arose in the same fashion just 210 years ago. The Waiho Loop 4 km north of the settlement of Franz Josef is the terminal moraine of Franz Josef Glacier, deposited by the retreating glacier about 12,000–3,000 years ago. An arc of rubble 80 m high, it was too rugged to be cleared for farming, and remains covered in native forest. Franz Josef Glacier exhibits
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#1732780204818984-488: A thin layer. A switch between the two flow conditions may be associated with surging behavior. Indeed, the loss of sub-glacial water supply has been linked with the shut-down of ice movement in the Kamb ice stream. The subglacial motion of water is expressed in the surface topography of ice sheets, which slump down into vacated subglacial lakes. The speed of glacial displacement is partly determined by friction . Friction makes
1066-410: A tremendous impact as the iceberg strikes the water. Tidewater glaciers undergo centuries-long cycles of advance and retreat that are much less affected by climate change than other glaciers. Thermally, a temperate glacier is at a melting point throughout the year, from its surface to its base. The ice of a polar glacier is always below the freezing threshold from the surface to its base, although
1148-481: A valley with temperate rain forest. Franz Josef Glacier currently terminates 19 km (12 mi) from the Tasman Sea . Near the end of the last ice age about 18,000 years ago it extended to the present-day coastline or even beyond. As it retreated the glacier left behind moraines of accumulated rock and chunks of ice which created coastal hills and lakes. Lake Wombat is a kettle lake created by ice left in
1230-769: A year. In December 1965, after 280 mm of rain in two days, the Waiho River broke out of the glacier and carried chunks of ice downriver. These were still up to 50 cm across when they reached the Tasman Sea 20 km downstream. Another flood destroyed the access road bridge in 1989, followed by a further flood in April 1991. Torrential rain destroyed the bridge across the Waiho River in March 2019, and it took 18 days to replace it. Westland Tai Poutini National Park
1312-468: Is a persistent body of dense ice that is constantly moving downhill under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries . It acquires distinguishing features, such as crevasses and seracs , as it slowly flows and deforms under stresses induced by its weight. As it moves, it abrades rock and debris from its substrate to create landforms such as cirques , moraines , or fjords . Although
1394-456: Is above or at freezing at the interface and is able to slide at this contact. This contrast is thought to a large extent to govern the ability of a glacier to effectively erode its bed , as sliding ice promotes plucking at rock from the surface below. Glaciers which are partly cold-based and partly warm-based are known as polythermal . Glaciers form where the accumulation of snow and ice exceeds ablation . A glacier usually originates from
1476-407: Is affected by factors such as slope, ice thickness, snowfall, longitudinal confinement, basal temperature, meltwater production, and bed hardness. A few glaciers have periods of very rapid advancement called surges . These glaciers exhibit normal movement until suddenly they accelerate, then return to their previous movement state. These surges may be caused by the failure of the underlying bedrock,
1558-411: Is because these peaks are located near or in the hyperarid Atacama Desert . Glaciers erode terrain through two principal processes: plucking and abrasion . As glaciers flow over bedrock, they soften and lift blocks of rock into the ice. This process, called plucking, is caused by subglacial water that penetrates fractures in the bedrock and subsequently freezes and expands. This expansion causes
1640-406: Is by basal sliding, where meltwater forms between the ice and the bed itself. Whether a bed is hard or soft depends on the porosity and pore pressure; higher porosity decreases the sediment strength (thus increases the shear stress τ B ). Porosity may vary through a range of methods. Bed softness may vary in space or time, and changes dramatically from glacier to glacier. An important factor
1722-434: Is called glaciology . Glaciers are important components of the global cryosphere . Glaciers are categorized by their morphology, thermal characteristics, and behavior. Alpine glaciers form on the crests and slopes of mountains. A glacier that fills a valley is called a valley glacier , or alternatively, an alpine glacier or mountain glacier . A large body of glacial ice astride a mountain, mountain range, or volcano
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#17327802048181804-416: Is called rock flour and is made up of rock grains between 0.002 and 0.00625 mm in size. Abrasion leads to steeper valley walls and mountain slopes in alpine settings, which can cause avalanches and rock slides, which add even more material to the glacier. Glacial abrasion is commonly characterized by glacial striations . Glaciers produce these when they contain large boulders that carve long scratches in
1886-647: Is higher, and the mountains above 5,000 m (16,400 ft) usually have permanent snow. Even at high latitudes, glacier formation is not inevitable. Areas of the Arctic , such as Banks Island , and the McMurdo Dry Valleys in Antarctica are considered polar deserts where glaciers cannot form because they receive little snowfall despite the bitter cold. Cold air, unlike warm air, is unable to transport much water vapor. Even during glacial periods of
1968-519: Is of good tramping track standard, but strenuous due to steeply climbing about 1,100 metres (3,600 ft) in height and considered "advanced" due to the duration of the hike. At the entrance of the valley lies the village of Franz Josef , which has a permanent population of approximately 330 residents. It is situated 5 km from the glacier on State Highway 6 and has a petrol station, small but busy heliport, numerous tourist accommodation options (with up to 2,000 people staying overnight during
2050-515: Is one of the few places in New Zealand with a full sequence of pristine landscape from mountain peaks to the sea. The retreat of Franz Josef Glacier has allowed native forest to colonise the bare rock left behind, and how long ago the glacier retreated can be read in the stage of plant succession present. Some bare rock was only exposed a decade ago, while other surfaces were exposed in 1951, 1830, 1750, and 1600. Fox and Franz Josef glaciers are
2132-402: Is predicted to retreat 5 kilometres (3.1 mi) and lose 38% of its mass by 2100 in a mid-range scenario of warming, although it may retreat as much as 8 kilometres (5.0 mi). There have been some incidents of jökulhlaups (outbreak floods from water-filled ice tunnels) at the glacier. The névés of Fox and Franz Josef glaciers has one of the world's highest precipitation levels: up to 15 m
2214-524: Is remarkably rapid, 15 or more feet a day. Airplane flights have proved a popular method of seeing this eight-mile long river of bluish-green ice , pressing down among hills that are aflame in January with red flowering rata trees. With Captain Mercer , I flew over the glacier and looked out toward the snow fields and bold Alps, and I also went with him on the initial air-mail route in New Zealand. Today
2296-897: Is termed an ice cap or ice field . Ice caps have an area less than 50,000 km (19,000 sq mi) by definition. Glacial bodies larger than 50,000 km (19,000 sq mi) are called ice sheets or continental glaciers . Several kilometers deep, they obscure the underlying topography. Only nunataks protrude from their surfaces. The only extant ice sheets are the two that cover most of Antarctica and Greenland. They contain vast quantities of freshwater, enough that if both melted, global sea levels would rise by over 70 m (230 ft). Portions of an ice sheet or cap that extend into water are called ice shelves ; they tend to be thin with limited slopes and reduced velocities. Narrow, fast-moving sections of an ice sheet are called ice streams . In Antarctica, many ice streams drain into large ice shelves . Some drain directly into
2378-413: Is the region where there is a net loss in glacier mass. The upper part of a glacier, where accumulation exceeds ablation, is called the accumulation zone . The equilibrium line separates the ablation zone and the accumulation zone; it is the contour where the amount of new snow gained by accumulation is equal to the amount of ice lost through ablation. In general, the accumulation zone accounts for 60–70% of
2460-402: Is the underlying geology; glacial speeds tend to differ more when they change bedrock than when the gradient changes. Further, bed roughness can also act to slow glacial motion. The roughness of the bed is a measure of how many boulders and obstacles protrude into the overlying ice. Ice flows around these obstacles by melting under the high pressure on their stoss side ; the resultant meltwater
2542-552: Is then forced into the cavity arising in their lee side , where it re-freezes. As well as affecting the sediment stress, fluid pressure (p w ) can affect the friction between the glacier and the bed. High fluid pressure provides a buoyancy force upwards on the glacier, reducing the friction at its base. The fluid pressure is compared to the ice overburden pressure, p i , given by ρgh. Under fast-flowing ice streams, these two pressures will be approximately equal, with an effective pressure (p i – p w ) of 30 kPa; i.e. all of
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2624-444: Is well illustrated by a postage stamp issued in 1946, depicting the view from St James Anglican Church . The church was built in 1931, with a panoramic altar window to take advantage of its location. By 1954, the glacier had disappeared from view from the church, but it reappeared briefly in 1997. Between 1983 and 2008 while most of the world's glaciers were retreating many New Zealand glaciers advanced; Franz Josef regained nearly half
2706-993: The Andes , the Himalayas , the Rocky Mountains , the Caucasus , Scandinavian Mountains , and the Alps . Snezhnika glacier in Pirin Mountain, Bulgaria with a latitude of 41°46′09″ N is the southernmost glacial mass in Europe. Mainland Australia currently contains no glaciers, although a small glacier on Mount Kosciuszko was present in the last glacial period . In New Guinea, small, rapidly diminishing, glaciers are located on Puncak Jaya . Africa has glaciers on Mount Kilimanjaro in Tanzania, on Mount Kenya , and in
2788-644: The Faroe and Crozet Islands were completely glaciated. The permanent snow cover necessary for glacier formation is affected by factors such as the degree of slope on the land, amount of snowfall and the winds. Glaciers can be found in all latitudes except from 20° to 27° north and south of the equator where the presence of the descending limb of the Hadley circulation lowers precipitation so much that with high insolation snow lines reach above 6,500 m (21,330 ft). Between 19˚N and 19˚S, however, precipitation
2870-760: The Himalayas , Andes , and a few high mountains in East Africa, Mexico, New Guinea and on Zard-Kuh in Iran. With more than 7,000 known glaciers, Pakistan has more glacial ice than any other country outside the polar regions. Glaciers cover about 10% of Earth's land surface. Continental glaciers cover nearly 13 million km (5 million sq mi) or about 98% of Antarctica 's 13.2 million km (5.1 million sq mi), with an average thickness of ice 2,100 m (7,000 ft). Greenland and Patagonia also have huge expanses of continental glaciers. The volume of glaciers, not including
2952-562: The Quaternary , Manchuria , lowland Siberia , and central and northern Alaska , though extraordinarily cold, had such light snowfall that glaciers could not form. In addition to the dry, unglaciated polar regions, some mountains and volcanoes in Bolivia, Chile and Argentina are high (4,500 to 6,900 m or 14,800 to 22,600 ft) and cold, but the relative lack of precipitation prevents snow from accumulating into glaciers. This
3034-535: The Rwenzori Mountains . Oceanic islands with glaciers include Iceland, several of the islands off the coast of Norway including Svalbard and Jan Mayen to the far north, New Zealand and the subantarctic islands of Marion , Heard , Grande Terre (Kerguelen) and Bouvet . During glacial periods of the Quaternary, Taiwan , Hawaii on Mauna Kea and Tenerife also had large alpine glaciers, while
3116-476: The Southern Alps to less than 300 metres (980 ft) above sea level. The area surrounding the two glaciers is part of Te Wāhipounamu , a World Heritage Site park. The Waiho River emerges from the glacier terminal of Franz Josef. The Māori name for the glacier is Kā Roimata o Hine Hukatere , literally: 'The tears of Hine Hukatere'. According to oral tradition, Hine Hukatere loved climbing in
3198-448: The 1990s and 2000s. In a study using data from January 1993 through October 2005, more events were detected every year since 2002, and twice as many events were recorded in 2005 as there were in any other year. Ogives or Forbes bands are alternating wave crests and valleys that appear as dark and light bands of ice on glacier surfaces. They are linked to seasonal motion of glaciers; the width of one dark and one light band generally equals
3280-547: The Franz Josef glacier area is the third-most-visited tourist spot in New Zealand, and one of the main tourist attractions on the West Coast . It had around 250,000 visitors a year in 2008, increasing to 700,000 a year (500,000 overnight) in 2017. It used to be possible to walk up to the glacier, but in March 2012 the terminal face of the glacier collapsed and it is now too dangerous to approach; signs warn against crossing
3362-558: The West Coast glaciers (believed to be Franz Josef) was made in the log of the ship Mary Louisa in 1859. The glacier was later named after Emperor Franz Joseph I of Austria by the German geologist Julius von Haast in 1865. Following the passage of the Ngāi Tahu Claims Settlement Act 1998 , the name of the glacier was officially altered to Franz Josef Glacier / Kā Roimata o Hine Hukatere . The névé or snowfield at
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3444-412: The advance of many alpine glaciers between 1950 and 1985, but since 1985 glacier retreat and mass loss has become larger and increasingly ubiquitous. Glaciers move downhill by the force of gravity and the internal deformation of ice. At the molecular level, ice consists of stacked layers of molecules with relatively weak bonds between layers. When the amount of strain (deformation) is proportional to
3526-520: The air from the snow turns it into "glacial ice". This glacial ice will fill the cirque until it "overflows" through a geological weakness or vacancy, such as a gap between two mountains. When the mass of snow and ice reaches sufficient thickness, it begins to move by a combination of surface slope, gravity, and pressure. On steeper slopes, this can occur with as little as 15 m (49 ft) of snow-ice. In temperate glaciers, snow repeatedly freezes and thaws, changing into granular ice called firn . Under
3608-430: The amount of melting at surface of the glacier, the faster the ice will flow. Basal sliding is dominant in temperate or warm-based glaciers. The presence of basal meltwater depends on both bed temperature and other factors. For instance, the melting point of water decreases under pressure, meaning that water melts at a lower temperature under thicker glaciers. This acts as a "double whammy", because thicker glaciers have
3690-713: The annual movement of the glacier. Ogives are formed when ice from an icefall is severely broken up, increasing ablation surface area during summer. This creates a swale and space for snow accumulation in the winter, which in turn creates a ridge. Sometimes ogives consist only of undulations or color bands and are described as wave ogives or band ogives. Glaciers are present on every continent and in approximately fifty countries, excluding those (Australia, South Africa) that have glaciers only on distant subantarctic island territories. Extensive glaciers are found in Antarctica, Argentina, Chile, Canada, Pakistan, Alaska, Greenland and Iceland. Mountain glaciers are widespread, especially in
3772-432: The bedrock has frequent fractures on the surface, glacial erosion rates tend to increase as plucking is the main erosive force on the surface; when the bedrock has wide gaps between sporadic fractures, however, abrasion tends to be the dominant erosive form and glacial erosion rates become slow. Glaciers in lower latitudes tend to be much more erosive than glaciers in higher latitudes, because they have more meltwater reaching
3854-445: The bedrock. By mapping the direction of the striations, researchers can determine the direction of the glacier's movement. Similar to striations are chatter marks , lines of crescent-shape depressions in the rock underlying a glacier. They are formed by abrasion when boulders in the glacier are repeatedly caught and released as they are dragged along the bedrock. The rate of glacier erosion varies. Six factors control erosion rate: When
3936-558: The construction of St James Church. Extract from the February 1936 issue of National Geographic Magazine : But the Franz Josef Glacier and its background of mountains is worth waiting long to see on a clear day. It is one of the most remarkable glaciers in the world. Slipping down from a large snowfield at more than 8,000 feet, it terminates in subtropical bush, only 700 feet above sea level. Movement in its upper reaches
4018-571: The created ice's density. The word glacier is a loanword from French and goes back, via Franco-Provençal , to the Vulgar Latin glaciārium , derived from the Late Latin glacia , and ultimately Latin glaciēs , meaning "ice". The processes and features caused by or related to glaciers are referred to as glacial. The process of glacier establishment, growth and flow is called glaciation . The corresponding area of study
4100-467: The deep profile of fjords , which can reach a kilometer in depth as ice is topographically steered into them. The extension of fjords inland increases the rate of ice sheet thinning since they are the principal conduits for draining ice sheets. It also makes the ice sheets more sensitive to changes in climate and the ocean. Although evidence in favor of glacial flow was known by the early 19th century, other theories of glacial motion were advanced, such as
4182-483: The deformation to become a plastic flow rather than elastic. Then, the glacier will begin to deform under its own weight and flow across the landscape. According to the Glen–Nye flow law , the relationship between stress and strain, and thus the rate of internal flow, can be modeled as follows: where: The lowest velocities are near the base of the glacier and along valley sides where friction acts against flow, causing
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#17327802048184264-418: The essentially correct explanation in the 1840s, although it was several decades before it was fully accepted. The top 50 m (160 ft) of a glacier are rigid because they are under low pressure . This upper section is known as the fracture zone and moves mostly as a single unit over the plastic-flowing lower section. When a glacier moves through irregular terrain, cracks called crevasses develop in
4346-475: The fracture zone. Crevasses form because of differences in glacier velocity. If two rigid sections of a glacier move at different speeds or directions, shear forces cause them to break apart, opening a crevasse. Crevasses are seldom more than 46 m (150 ft) deep but, in some cases, can be at least 300 m (1,000 ft) deep. Beneath this point, the plasticity of the ice prevents the formation of cracks. Intersecting crevasses can create isolated peaks in
4428-509: The glacial base and facilitate sediment production and transport under the same moving speed and amount of ice. Material that becomes incorporated in a glacier is typically carried as far as the zone of ablation before being deposited. Glacial deposits are of two distinct types: St James Church, Franz Josef Too Many Requests If you report this error to the Wikimedia System Administrators, please include
4510-453: The glacier to melt, creating a water source that is especially important for plants, animals and human uses when other sources may be scant. However, within high-altitude and Antarctic environments, the seasonal temperature difference is often not sufficient to release meltwater. Since glacial mass is affected by long-term climatic changes, e.g., precipitation , mean temperature , and cloud cover , glacial mass changes are considered among
4592-428: The glacier will be accommodated by motion in the sediments, or if it'll be able to slide. A soft bed, with high porosity and low pore fluid pressure, allows the glacier to move by sediment sliding: the base of the glacier may even remain frozen to the bed, where the underlying sediment slips underneath it like a tube of toothpaste. A hard bed cannot deform in this way; therefore the only way for hard-based glaciers to move
4674-510: The glacier's surface area, more if the glacier calves icebergs. Ice in the accumulation zone is deep enough to exert a downward force that erodes underlying rock. After a glacier melts, it often leaves behind a bowl- or amphitheater-shaped depression that ranges in size from large basins like the Great Lakes to smaller mountain depressions known as cirques . The accumulation zone can be subdivided based on its melt conditions. The health of
4756-451: The glacier's unusually fast flow, and some walks including passages through ice tunnels, they are still considered quite safe and only somewhat strenuous. In June 2010, an Australian tourist died of a heart attack during a guided hike of the glacier. An alternative option to view the glacier is via the 8-hour day hike up the 1,303 metres (4,275 ft) high Alex Knob, overlooking the Franz Josef Glacier and valley below. The path up Alex Knob
4838-558: The head of Franz Josef Glacier is over 2,500 metres (8,200 ft) above sea level and 20 square kilometres (7.7 sq mi) in area. This wide névé, which is over 300 metres (980 ft) deep, feeds large amounts of compacted snow into a steep and narrow valley which drops quickly to very low altitudes: the glacier descends to 300 metres (980 ft) above sea level in just 11 km (6.8 mi). This combination of factors leads to Franz Josef persisting where most temperate-zone glaciers would have already melted, and allows it to share
4920-619: The ice at the bottom of the glacier move more slowly than ice at the top. In alpine glaciers, friction is also generated at the valley's sidewalls, which slows the edges relative to the center. Mean glacial speed varies greatly but is typically around 1 m (3 ft) per day. There may be no motion in stagnant areas; for example, in parts of Alaska, trees can establish themselves on surface sediment deposits. In other cases, glaciers can move as fast as 20–30 m (70–100 ft) per day, such as in Greenland's Jakobshavn Isbræ . Glacial speed
5002-476: The ice it had lost over the previous century. This anomalous growth has been attributed not to increased rainfall but to a series of cool years caused by increased southerly air flow in the Tasman sea. After 2008 the glacier entered a very rapid phase of retreat, shrinking by 1.5 km between 2008 and 2017. It is now once again 3 km shorter than it was 100 years ago. Based on these patterns, Franz Josef Glacier
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#17327802048185084-420: The ice sheets of Antarctica and Greenland, has been estimated at 170,000 km . Glacial ice is the largest reservoir of fresh water on Earth, holding with ice sheets about 69 percent of the world's freshwater. Many glaciers from temperate , alpine and seasonal polar climates store water as ice during the colder seasons and release it later in the form of meltwater as warmer summer temperatures cause
5166-556: The ice to act as a lever that loosens the rock by lifting it. Thus, sediments of all sizes become part of the glacier's load. If a retreating glacier gains enough debris, it may become a rock glacier , like the Timpanogos Glacier in Utah. Abrasion occurs when the ice and its load of rock fragments slide over bedrock and function as sandpaper, smoothing and polishing the bedrock below. The pulverized rock this process produces
5248-488: The ice, called seracs . Crevasses can form in several different ways. Transverse crevasses are transverse to flow and form where steeper slopes cause a glacier to accelerate. Longitudinal crevasses form semi-parallel to flow where a glacier expands laterally. Marginal crevasses form near the edge of the glacier, caused by the reduction in speed caused by friction of the valley walls. Marginal crevasses are largely transverse to flow. Moving glacier ice can sometimes separate from
5330-411: The idea that meltwater, refreezing inside glaciers, caused the glacier to dilate and extend its length. As it became clear that glaciers behaved to some degree as if the ice were a viscous fluid, it was argued that "regelation", or the melting and refreezing of ice at a temperature lowered by the pressure on the ice inside the glacier, was what allowed the ice to deform and flow. James Forbes came up with
5412-418: The increased pressure can facilitate melting. Most importantly, τ D is increased. These factors will combine to accelerate the glacier. As friction increases with the square of velocity, faster motion will greatly increase frictional heating, with ensuing melting – which causes a positive feedback, increasing ice speed to a faster flow rate still: west Antarctic glaciers are known to reach velocities of up to
5494-423: The infrared OH stretching mode of the water molecule. (Liquid water appears blue for the same reason. The blue of glacier ice is sometimes misattributed to Rayleigh scattering of bubbles in the ice.) A glacier originates at a location called its glacier head and terminates at its glacier foot, snout, or terminus . Glaciers are broken into zones based on surface snowpack and melt conditions. The ablation zone
5576-525: The main season) and a number of restaurants and shops. Just south of the village, a sealed road leads from the highway into the Franz Josef Glacier valley and to a car park. Several small walks start from the Valley Road and the car park, and it is also possible to comfortably cycle from Franz Josef township to the car park. Glacier A glacier ( US : / ˈ ɡ l eɪ ʃ ər / ; UK : / ˈ ɡ l æ s i ər , ˈ ɡ l eɪ s i ər / )
5658-679: The most deformation. Velocity increases inward toward the center line and upward, as the amount of deformation decreases. The highest flow velocities are found at the surface, representing the sum of the velocities of all the layers below. Because ice can flow faster where it is thicker, the rate of glacier-induced erosion is directly proportional to the thickness of overlying ice. Consequently, pre-glacial low hollows will be deepened and pre-existing topography will be amplified by glacial action, while nunataks , which protrude above ice sheets, barely erode at all – erosion has been estimated as 5 m per 1.2 million years. This explains, for example,
5740-528: The most publicly-accessible glaciers in New Zealand, and among the most accessible in the world – until recently, there was easy walking access directly to the glacier termini. Consequently for over a century they have been a significant tourist attraction. The glacier is associated with the Graham family, in particular mountaineers and guides Alec and Peter Graham and Rose Graham and historian Dorothy Fletcher (née Graham). Services in their hotel brought about
5822-445: The most sensitive indicators of climate change and are a major source of variations in sea level . A large piece of compressed ice, or a glacier, appears blue , as large quantities of water appear blue , because water molecules absorb other colors more efficiently than blue. The other reason for the blue color of glaciers is the lack of air bubbles. Air bubbles, which give a white color to ice, are squeezed out by pressure increasing
5904-468: The mountains and persuaded her lover Tuawe to climb with her. Tuawe was a less experienced climber than Hine Hukatere but loved to accompany her, until an avalanche swept him from the peaks to his death. Hine Hukatere was broken-hearted and her many, many tears flowed down the mountain. Rangi the Sky Father took pity on her and froze them to form the glacier. The first European description of one of
5986-725: The pooling of meltwater at the base of the glacier — perhaps delivered from a supraglacial lake — or the simple accumulation of mass beyond a critical "tipping point". Temporary rates up to 90 m (300 ft) per day have occurred when increased temperature or overlying pressure caused bottom ice to melt and water to accumulate beneath a glacier. In glaciated areas where the glacier moves faster than one km per year, glacial earthquakes occur. These are large scale earthquakes that have seismic magnitudes as high as 6.1. The number of glacial earthquakes in Greenland peaks every year in July, August, and September and increased rapidly in
6068-410: The pressure of the layers of ice and snow above it, this granular ice fuses into denser firn. Over a period of years, layers of firn undergo further compaction and become glacial ice. Glacier ice is slightly more dense than ice formed from frozen water because glacier ice contains fewer trapped air bubbles. Glacial ice has a distinctive blue tint because it absorbs some red light due to an overtone of
6150-399: The safety barriers at the lookout. As of 2023, the valley walk ends at a lookout about 3000 m from the main terminal face of the glacier. Visiting the glacier now requires a helicopter flight past the unstable terminal face. Glacier walks also require some specialised equipment, namely ice axes and crampons that latch onto a sturdy boot. These are usually provided by tour companies. As
6232-567: The sea, often with an ice tongue , like Mertz Glacier . Tidewater glaciers are glaciers that terminate in the sea, including most glaciers flowing from Greenland, Antarctica, Baffin , Devon , and Ellesmere Islands in Canada, Southeast Alaska , and the Northern and Southern Patagonian Ice Fields . As the ice reaches the sea, pieces break off or calve, forming icebergs . Most tidewater glaciers calve above sea level, which often results in
6314-409: The stagnant ice above, forming a bergschrund . Bergschrunds resemble crevasses but are singular features at a glacier's margins. Crevasses make travel over glaciers hazardous, especially when they are hidden by fragile snow bridges . Below the equilibrium line, glacial meltwater is concentrated in stream channels. Meltwater can pool in proglacial lakes on top of a glacier or descend into the depths of
6396-423: The stress being applied, ice will act as an elastic solid. Ice needs to be at least 30 m (98 ft) thick to even start flowing, but once its thickness exceeds about 50 m (160 ft) (160 ft), stress on the layer above will exceeds the inter-layer binding strength, and then it'll move faster than the layer below. This means that small amounts of stress can result in a large amount of strain, causing
6478-438: The surface snowpack may experience seasonal melting. A subpolar glacier includes both temperate and polar ice, depending on the depth beneath the surface and position along the length of the glacier. In a similar way, the thermal regime of a glacier is often described by its basal temperature. A cold-based glacier is below freezing at the ice-ground interface and is thus frozen to the underlying substrate. A warm-based glacier
6560-446: The walking part of any tour up to the glacier takes a long time, and ends at the first icefall (a frozen waterfall, draping a natural step in the land underneath), many tourists book helicopter tours from one of the several local airlines, which usually drop their guests between the first and second icefalls, for a guided 1–2 hour walk through the broken ground atop the glacier. Although the glacial landscape changes almost daily, given
6642-417: The weight of the ice is supported by the underlying water, and the glacier is afloat. Glaciers may also move by basal sliding , where the base of the glacier is lubricated by the presence of liquid water, reducing basal shear stress and allowing the glacier to slide over the terrain on which it sits. Meltwater may be produced by pressure-induced melting, friction or geothermal heat . The more variable
6724-478: The western face of the Main Divide, and Franz Josef glacier being short and steep is more sensitive to increased snow in the névé than other glaciers. If the increased precipitation falls as snow, the glacier will advance; if as rain, it will retreat. Increased snowfall takes around 5–6 years to result in changes in the terminus location. Franz Josef Glacier advanced rapidly during the Little Ice Age , reaching
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